Ray Peat on Light and Red Light

Short answer: Ray Peat called darkness one of our major stressors. He wrote that light, especially red and orange light, activates the respiratory enzyme in the mitochondria, while long nights and winters raise cortisol and suppress the thyroid.

What Ray Peat wrote about light

Darkness suppresses mitochondrial function and light activates it. Prolonged darkness raises cortisol. Source: Stem cells, cell culture, and culture: Issues in regeneration, Growth hormone: Hormone of Stress, Aging, and Death?

Red and orange wavelengths pass deep into tissue because water absorbs them only weakly. There they reach the enzyme cytochrome oxidase, which red light activates or reactivates, increasing ATP production. Source: Cataracts: water, energy, light, and aging

That effect counteracts the toxic effects of ultraviolet light. Source: Cataracts: water, energy, light, and aging

Winter darkness is stressful in a fundamental way and tends to suppress thyroid function. He observed that hamsters' thymus glands shrank in winter and regrew in summer. Source: Multiple Sclerosis and other hormone related brain syndromes

He counted winter sickness, with lethargy and weight gain, and the stress of the night as forms of the same respiratory defect. Source: Mitochondria and mortality

He listed red light with niacinamide, progesterone, sugar and carbon dioxide as protective factors, and with magnesium and sleep for protecting the aging brain. Source: Cancer: Disorder and Energy, Rosacea, inflammation, and aging: The inefficiency of stress, Alzheimer's: The problem of Alzheimer's disease as a clue to immortality — part 2

For premenstrual syndrome, extra light was the first of the things he found helpful. Source: Multiple Sclerosis and other hormone related brain syndromes

What he suggested in practice

• Bright light during the day, weak in blue and with protection from ultraviolet.
• More light in winter.
• He connected light and carbon dioxide: both keep oxidative metabolism going and hold lactic acid down.

Where he wrote about it

This topic comes up in 38 of the articles on his site. These are the most relevant ones:

• Aging Eyes, Infant Eyes, and Excitable Tissues · original on raypeat.com ↗
• Stem cells, cell culture, and culture: Issues in regeneration · original on raypeat.com ↗
• The transparency of life: Cataracts as a model of age-related disease · original on raypeat.com ↗
• Cataracts: water, energy, light, and aging · original on raypeat.com ↗
• Multiple Sclerosis and other hormone related brain syndromes · original on raypeat.com ↗
• The dark side of stress (learned helplessness) · original on raypeat.com ↗
• Rosacea, inflammation, and aging: The inefficiency of stress · original on raypeat.com ↗
• Bleeding, clotting, cancer · original on raypeat.com ↗

My take

Sun is at the top of my list. Red light on my stomach improves digestion, lowers inflammation and reverses bloating, and I use heat lamps after sunset.

Quick answers

What did Ray Peat say about red light?

That red and orange light penetrate tissue and activate cytochrome oxidase, the respiratory enzyme, increasing ATP production and offsetting ultraviolet damage.

What did Ray Peat say about darkness?

He called it one of our major stressors: it suppresses mitochondrial function, raises cortisol and, in winter, suppresses the thyroid.